A brake system for a motor vehicle is described in German Application No. DE 10 2008 044 002 A1. The brake system has a hydraulic brake booster having a pressure accumulator which is chargeable with the aid of a pump, and which via a pressure build-up valve is hydraulically connected to a booster cylinder situated between a brake pedal and a brake master cylinder of the brake system. The aim is to allow a pressure that is present in the booster cylinder to be increased by at least partially opening the pressure build-up valve. In this way, at least one displaceable piston mounted in the brake master cylinder may be acted on by an additional force for increasing a pressure that is present in the brake master cylinder.